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1 Chapter 4 Rice Stand Establishment Charles E. Wilson, Jr., Yeshi Wamishe, Gus Lorenz and Jarrod Hardke S tand establishment is the first step to a successful correct seeding rate for different seeding dates and rice crop. Factors that influence stand establish- methods, soils, seedbed conditions and cultivars. This ment include cultivar, seedling vigor, seeding program is available at local county Extension offices or method, seeding date, soil properties, seeding rate, seed may be accessed online from the Cooperative Extension treatments, environment and geographic location. Later Service web site at http://riceseed.uaex.edu/. management decisions are affected by stand density and uniformity. The goal of stand establishment is to obtain Table 4-1 provides a list of seed weights and seeding a uniform stand of healthy rice seedlings. Uniformity rates needed to obtain the different number of seeds of emergence is important for accuracy of the DD50 per square foot for commonly grown cultivars. Under program, pesticide application timing, drain timing most conditions where rice is drill-seeded, 30 seeds per for straighthead prevention, milling yield, irrigation square foot are adequate to obtain the optimum stand termination, yield and harvest. density of 10 to 20 plants per square foot for con- ventional varieties (or 6 to 13 seedlings per 7.5-inch drill row foot). For hybrids, 10 to 15 seeds per square Seeding Rate foot is needed to obtain optimum stand density of 6 to Seeding rates vary depending on cultivar, due to 10 plants per square foot (or 4 to 6 seedlings per 7.5- differences in seed size and/or weight. The RICESEED inch drill row foot). Stand densities above the optimum program is available to assist growers in determining the density increase disease, plant height and lodging. Table 4-1. Seeding rates for different seeds per square foot based on seed weight. Seed Number of Seed/Sq. Ft. Cultivar Weight Seeds/lb 10 15 20 25 30 35 40 45 50 Seeding Rate, lbs/A Bengal 27.4 16,569 -- -- 53 66 79 92 105 118 131 Caffey 28.7 15,813 -- -- 55 69 83 96 110 124 138 Cheniere 21.8 20,826 -- -- 42 52 63 73 84 94 105 CL111 26.0 17,462 -- -- 50 62 75 87 100 112 125 CL131 21.9 20,731 -- -- 42 53 63 74 84 95 105 CL142 AR 25.9 17,529 -- -- 50 62 75 87 99 112 124 CL151 23.3 19,485 -- -- 45 56 67 78 89 101 112 CL152 20.5 22,190 -- -- 39 49 59 69 79 88 98 CL162 MS 25.9 17,529 -- -- 50 62 75 87 99 112 124 CL261 24.6 18,455 -- -- 47 59 71 83 94 106 118 Grams per 1,000 grains or milligrams per seed. (Continued) 31

2 Table 4-1. Seeding rates for different seeds per square foot based on seed weight. Seed Number of Seed/Sq. Ft. Cultivar Weight Seeds/lb 10 15 20 25 30 35 40 45 50 Seeding Rate, lbs/A Cocodrie 25.6 17,734 -- -- 49 61 74 86 98 111 123 Francis 22.8 19,912 -- -- 44 55 66 77 88 98 109 Jazzman 25.2 18,016 -- -- 48 60 73 85 97 109 121 JES 26.5 17,132 -- -- 51 64 76 89 102 114 127 Jupiter 25.8 17,597 -- -- 50 62 74 87 99 111 124 Mermentau 23.3 19,460 -- -- 45 56 67 78 90 101 112 Presidio 24.3 18,683 -- -- 47 58 70 82 93 105 117 Rex 27.6 16,449 -- -- 53 66 79 93 106 119 132 RT CL XL729 21.79 20,835 21 31 42 -- -- -- -- -- -- RT CL XL745 21.70 20,922 21 31 42 -- -- -- -- -- -- RT XL723 21.14 21,476 20 30 41 -- -- -- -- -- -- RT XL753 20.50 22,146 20 30 39 -- -- -- -- -- -- Roy J 22.9 19,825 -- -- 44 55 66 77 88 99 110 Taggart 27.4 16,569 -- -- 53 66 79 92 105 118 131 Templeton 22.7 20,000 -- -- 44 54 65 76 87 98 109 Wells 25.2 18,016 -- -- 48 60 73 85 97 109 121 Grams per 1,000 grains or milligrams per seed. Below optimum stand densities are capable of CL151 and CL161 by reducing the risk of excessive producing high yields provided that plant distribu- plant populations. tion is uniform, weeds are controlled and additional nitrogen is applied to increase tillering. Most cultivars Table 4-2. Influence of seeding rate on grain yields compensate for low seedling population by increasing of five rice varieties averaged across five locations tillering and the number of grains per panicle. in 2004 and 2005. Seeding rates should be increased by 10 percent for Seed Grain Yield no-till seedbeds and early seeding; 20 percent for Rate Bengal CL161 Francis Wells broadcast seeding, poor seedbed condition or clay lbs/acre bu/A soils; and 30 percent for water-seeding. In fields with 45.0 154 135 132 141 a history of severe infestations of grape colaspis larvae 67.5 160 136 136 144 (lespedeza worm) or fields with chronic infestations, 90.0 159 143 155 145 seeding rates should be increased to help compensate 112.5 163 146 141 147 or use a recommended seed treatment insecticide. 135.0 161 149 144 147 The recommended seeding rate of 30 seeds per LSD 22 square foot for conventional varieties is a reduction Source: Runsick et al., 2006. p. 304-309. B.R. Wells Rice Res. Studies 2005. Ark. Agr. Exp. Sta. Res. Ser. 540. from previous recommendations. Recent studies suggest that seeding rates may be reduced by 25 per- cent from older recommendations and still obtain Management Key optimum yields (Table 4-2). Seeding rates as low as 67.5 pounds per acre (1.5 bushels/acre) result in Use the RICESEED program to calculate optimum grain yields and milling yields similar to those seeding rates for specific fields to avoid excessive obtained with higher seeding rates. Reduced seeding plant populations. Proper calibration of drills is an rates lower the potential for sheath blight and the important step in obtaining optimum seeding rates. amount of fungicide needed on varieties such as 32

3 Recommended drill row widths for rice are between 4 (Table 4-3). However, other practical considerations and 10 inches. Limited research data suggests that should be made regarding row spacing. For example, under most conditions row widths between 4 and 10 wider row spacing is desirable on clay soils where inches can produce similar yields. However, as row clods may become lodged between the coulters on width increases, the importance of uniform stand narrow row drills. Seeding rates do not need to be density also increases. Several studies show a trend for adjusted for differences in drill row widths in the 4- to higher grain yields with narrower drill row spacing, 10-inch range. Table 4-4 provides the number of seed thus a drill row spacing of 6 to 8 inches is ideal per row foot for 6- to 10-inch drill row spacing and seeding rates for drill calibration. Table 4-3. Influence of row spacing on grain yields of three rice varieties at three locations during 2004. Seed Treatments Grain Yield Seed treatments are often considered insurance and Cultivar RREC SEREC Lake Hogue include fungicides, fertilizers, growth regulators and 7" 10" 7" 10" 7" 10" insecticides (when available). Although most seed bu/A treatments are generally inexpensive, they are not Banks 190 170 173 162 169 160 always recommended. The decision to use seed treat- Cybonnet 169 150 128 125 175 166 ments should be based on planting date, tillage/plant- Francis 206 180 160 154 213 193 ing method, cultivar, soil texture, disease problems RREC = Rice Research and Extension Center, Stuttgart; SEREC = and field history. Most seed treatments are for use Southeast Research and Extension Center, Rohwer; and Lake only by commercial seed treaters, although a few are Hogue = Poinsett County. available as planter box treatments. Source: Frizzell et al., 2006. p. 270-275. B.R. Wells Rice Res. Studies 2005. Ark. Agr. Exp. Sta. Res. Ser. 540. Fungicide seed treatments (Table 4-5) are generally recommended for early planting, clay soils, reduced Table 4-4. Seed spacing for calibration drills. tillage (especially no-till) or on fields that have a Seeds/ Seed Per Row Foot for history of poor seedling emergence and seedling Different Row Spacings disease. Under the right conditions, fungicide seed Sq. Ft. 6" 7" 8" 9" 10" treatments can result in a 10 to 20 percent stand 20 10 12 13 15 17 increase over untreated seed. However, there may not 30 15 17 20 23 25 be a yield increase since rice can compensate for thin, 40 20 23 27 30 33 uniform stands by increased tillering. Fungicide seed 50 25 29 33 38 42 treatments do not speed the rate of emergence like growth regulator treatments, nor do they control 60 30 35 40 45 50 kernel or false smut. The use of fungicide-treated seed 70 35 41 47 53 58 also does not guarantee that seedling disease will not 80 40 45 54 60 68 impact stand density, especially three to four weeks Table 4-5. Fungicide seed treatment products and disease control spectrum for rice. Active Disease Fungicide Ingredient Rate/cwt seed Comments Allegiance FL metalaxyl 0.75 - 1.5 fl oz Apply with commercial seed-treating equipment. (formerly Apron) Apron XL LS mefenoxam 0. 32 - 0.64 fl oz Apply with commercial seed-treating equipment. Use higher rates for early planting or other Pythium diseases severe disease situations. EverGol Energy prothioconazole 1 - 2 fl oz Must use high rate for moderate to high + penflufen seedling disease pressure. + metalaxyl Specific product labels should be consulted for use rates and precautions. Some products may be mixed to broaden the spectrum of seed protection. The highest labeled rates should be used for very early planting or other situations where seed germination and emergence may be delayed by environmental conditions. The effectiveness of most products is relatively short-lived under field conditions, providing about 2 to 3 weeks of seed protection at most. (Table continued) 33

4 Table 4-5. Fungicide seed treatment products and disease control spectrum for rice. (cont.) Active Disease Fungicide Ingredient Rate/cwt seed Comments RTU-Vitavax- carboxin 5.0 - 6.8 fl oz Apply with commercial seed-treating equipment Thiram + thriam or use as a pour-on hopper box treatment. Rhizoctonia Maxim 4FS fludioxonil 0.08 - 0.16 fl oz Apply with commercial seed-treating equipment. seedling diseases, Use higher rate for severe disease situations. general seed rots EverGol Energy prothioconazole 1 - 2 fl oz Must use high rate for moderate to high seedling + penflufen disease pressure. + metalaxyl RTU-Vitavax- carboxin 5.0 - 6.8 fl oz Apply with commercial seed-treating equipment Thiram + thriam or use as a pour-on hopper box treatment. Allegiance FL or metalaxyl 0.75 - 1.5 fl oz Apply with commercial seed-treating equipment. Apron XL or or mefenoxam 0.32 - 0.64 fl oz Apron XL LS mefenoxam 0.32 - 0.64 fl oz Apply with commercial seed-treating equipment. + Maxim 4FS + fludioxonil + 0.08 - 0.16 fl Use higher rates for early planting or severe oz disease situations. Dynasty azoxystrobin 0.153 - 1.53 fl oz Commercial seed treaters only. Usually sold with Apron XL and Maxim on rice to improve seedling disease control. To reduce seedborne Pythium, blast, data suggests rates of Dynasty above Rhizoctonia, 0.75 fl oz per cwt. The use of a seed treatment general seed rot fungicide does not mean complete control of the disease later in the season and the field should still be scouted for blast disease and managed with deeper flood and foliar fungi- cides. May be included as part of CruiserMaxx Rice seed treatment. Trilex 2000 trifloxystrobin 1 2 - fl oz See label. + metalaxyl EverGol Energy prothioconazole 1 - 2 fl oz Must use high rate for moderate to high seedling + penflufen disease pressure. + metalaxyl This information was current as of October 1, 2013 and applies only to Arkansas and may not be appropriate for other states or locations. The listing of any product in this publication does not imply endorsement of that product or discrimination against any other product by the University of Arkansas Division of Agriculture. Every effort was made to ensure accuracy, but the user of any crop protection product must read and follow the most current label on the product - The Label is the Law. For further assistance, contact the local Cooperative Extension Service office. Specific product labels should be consulted for use rates and precautions. Some products may be mixed to broaden the spectrum of seed protection. The highest labeled rates should be used for very early planting or other situations where seed germination and emergence may be delayed by environmental conditions. The effectiveness of most products is relatively short-lived under field conditions, providing about 2 to 3 weeks of seed protection at most. after planting. Most fungicide seed treatments are are not recommended for water-seeded rice. The use specific for certain groups of fungi that may cause of GA3 is highly recommended for semi-dwarf rice stand loss. Refer to MP154, Plant Disease Control cultivars, cultivars having poor seedling vigor, on clay Products Handbook (http://www.uaex.edu/Other_Areas/ soils, reduced tillage situations and early seeding dates. publications/HTML/MP-154.asp), for the latest Use of GA3 treated seed may increase uniformity of information on fungicide seed treatments. emergence, minimize the effects of deep seed place- ment and speed up germination and emergence and Recommended growth regulator seed treatments are has been well researched since 1988. Growth regulator currently limited to gibberellic acid (or GA3) products seed treatments may be used in combination with which include Release and GibGro. Seed treatments other types of seed treatments, but always check the containing GA3 do not prevent seedling disease and product labels for mixing instructions and precautions 34

5 prior to use. When treated with GA3, rice seedlings Insecticide seed treatments (Table 4-6) are may appear tall and yellow shortly after emergence. recommended for fields with a history of grape Seedlings normally outgrow these symptoms within colaspis or rice water weevil or soil types most com- one or two weeks after emergence. If a stand failure monly associated with these insects (silt loam for occurs and a residual herbicide has been used, check grape colaspis). Even in the absence of insect pressure, the herbicide and GA3 product labels for replanting insecticide seed treatments have generally been restrictions/recommendations with GA3-treated seed. observed to increase seedling emergence and early For example, the Prowl herbicide label recommends season vigor and can sometimes increase yield. Refer that GA3-treated seed not be used to replant fields that to MP144, Insecticide Recommendations for Arkansas have been treated with Prowl. (http://www.uaex.edu/Other_Areas/publications/PDF/ MP144/MP-144.asp) for the latest information on insecticide seed treatments. Management Key Use gibberellic acid (GA3) seed treatments when Seeding Date and Soil the following conditions exist: Temperatures Semi-dwarf rice cultivars Cultivars with poor seedling vigor The daily maximum, mean and minimum soil Rice planted on clay soils temperatures measured at a 4-inch depth at three Reduced tillage rice production University of Arkansas Division of Agriculture Early-planted rice Experiment Stations are provided in Table 4-7. Rice should be seeded in a seedbed that is conducive to The use of fertilizer (i.e., Zn) seed treatments is good seed-to-soil contact when the daily average soil addressed in later chapters that concern fertilization temperature at the 4-inch depth is above 60F. Soil practices. Check with your local county Extension temperature measurements taken from Rohwer, office for the most recent recommendations for use of Stuttgart and Keiser indicate that the average soil new seed treatment products. temperature at a 4-inch depth reaches 60F about Table 4-6. Insecticide seed treatment products and insect control spectrum for rice. Insecticide Active Ingredient Rate/cwt seed Comments Dermacor X-100 chlorantraniliprole 1.5 - 6.0 fl oz Control of rice water weevil larvae. Suppression only of grape (see label) colaspis larvae. 24c Special Local Need label for use in water- seeded rice until June 5, 2018. See label. NipsIt INSIDE 5 FS clothianidin 1.92 fl oz Control of rice water weevil and grape colaspis larvae. Use only on dry-seeded rice. DO NOT spray crop with another neonicotinoids insecticide after using NipsIt INSIDE. DO NOT use near fish or crawfish farms. CruiserMaxx Rice thiamethoxam 7.0 fl oz Control of rice water weevil and grape colaspis larvae. DO NOT plant or sow Cruiser-treated seed by aerial application. Cruiser is NOT labeled for use in water-seeded rice. DO NOT use treated fields for aquaculture of edible fish or crustaceans. DO NOT exceed 120 lbs seed per acre. This information was current as of October 1, 2013 and applies only to Arkansas and may not be appropriate for other states or locations. The listing of any product in this publication does not imply endorsement of that product or discrimination against any other product by the University of Arkansas Division of Agriculture. Every effort was made to ensure accuracy, but the user of any crop protection product must read and follow the most current label on the product - The Label is the Law. For further assistance, contact the local Cooperative Extension Service office. Specific product labels should be consulted for use rates and precautions. Some products may be mixed to broaden the spectrum of seed protection. The highest labeled rates should be used for very early planting or other situations where seed germination and emergence may be delayed by environmental conditions. The effectiveness of most products is relatively short-lived under field conditions, providing about 2 to 3 weeks of seed protection at most. 35

6 Table 4-7. Minimum, maximum and mean undisturbed soil temperatures at a 4-inch depth for selected dates at three locations in Arkansas. Location Rohwer, SEREC Stuttgart, RREC Keiser, NEREC Latitude 33.45 N 34.49 N 35.68 N Soil Texture Perry Clay DeWitt Silt Loam Sharkey Clay Daily Temp. Min Max Mean Min Max Mean Min Max Mean Date 4 inch undisturbed soil temperature, F March 15 50 57 54 46 56 51 44 54 49 April 1 53 52 57 49 62 55 46 55 51 April 15 60 69 64 56 69 63 55 64 59 May 1 63 74 69 59 71 65 58 69 64 May 15 69 75 72 66 79 72 64 81 73 May 31 69 78 74 69 78 73 70 74 72 Temperatures are the six-year average from 1990 to 1995. Temperatures are the nine-year average from 1990 to 1998. April 8, 11 and 16, respectively. Assuming adequate seeding date studies conducted during the past moisture for germination, rice emergence should 10 years suggest these cultivar selection guidelines occur within approximately 8, 14 and 20 days after were not appropriate for late seeding. Depending on seeding when 4-inch soil temperatures average 70, environmental conditions, cultivars with longer grow- 65 and 60F, respectively (based on data from ing seasons may produce higher yields than very seeding date studies). short-season cultivars when seeded late. Cultivar selec- tion decisions for late-planted rice should be made based on cultivar performance in seeding date studies. Management Key Results from annual seeding date studies are published Seeding when the average soil temperature at the each year in Rice Information Sheets that summarize 4-inch depth is above 60F enhances uniform cultivar yield performance among different locations emergence and reduction in potential for and seeding dates. seedling diseases. Table 4-8. General seeding, seedling emergence and flooding date information for the DD50 seeding When rice is planted early, more time is required date study in 2010 at the Rice Research and Extension Center near Stuttgart, Arkansas. for germination, emergence and development to the Seeding Date 5-leaf stage. For example, in the 2010 Rice DD50 Parameter March 31 April 19 May 12 June 10 Research and Development Studies, 20 rice cultivars Emergence seeded on March 31 required an average of 10 days date April 10 May 2 May 18 June 17 from seeding to emergence and an additional 34 days Flood date May 14 May 26 June 16 July 9 to reach the 5-leaf stage for flooding (Table 4-8). In Days from comparison, rice planted June 5 only required 7 days seeding to for emergence and an additional 22 days to reach the emergence 10 13 6 7 5-leaf growth stage. The extended time between Days from seeding planting and flooding at the 5-leaf growth stage may to flooding 44 37 35 29 increase production costs associated with flushing and Days from weed control. emergence to flooding 34 24 29 22 Specific beginning and ending seeding dates were Source: : Frizzell et al., 2011. B.R. Wells Rice Res. Studies 2012. Ark. Agr. Exp. Sta. Res. Ser. once suggested, by cultivar, for the geographic regions of south, central and north Arkansas. However, 36

7 Table 4-9. Predicted relative yield potential for drill- Management Key seeded rice in central Arkansas by seeding date. Actual Rice planted within the early window (Table 4-9) Relative Yield Yield performs better than rice planted in later windows; Potential Potential Seeding Date Range however, there may be increased stand establishment % bu/A Begin Cut-off risks in some fields planted at the earliest dates due 95.0-100.0 166-175 March 23 May 20 to cool, wet soil conditions. 90.0-94.9 158-165 May 21 June 1 85.0-89.9 149-157 June 2 June 11 Seeding date studies conducted at the Rice Research 80.0-84.9 140-148 June 11 June 18 and Extension Center (RREC), located near Stuttgart, 70.0-79.9 123-139 June 19 June 30 Arkansas, were analyzed to predict the optimum Actual yield potential is based on a 100% relative grain yield of 175 bu/A at 12% moisture. seeding dates for central Arkansas (Table 4-9). The Considered optimum seeding date based on potential grain yield optimum seeding date range was defined as seeding and does not consider other management risks or milling yield potential. dates producing 95 to 100 percent yield potential. Seeding date and relative yield potential are based on a quadratic relationship described by the equation % relative yield = 22.4 + Results suggest that the optimum time period for drill- 1.33x - 0.006x2 (where x = Julian date or day number of year, where seeded rice in most years, based solely on grain yields, April 20 = day 110). in central Arkansas is March 23 to May 20 (Table 4-9). Source: Slaton et al. 1991. Growers must be cautioned that risk factors increase Table 4-10. General suggested optimum and for very early seeding dates. These risk factors include, recommended seeding dates for south, central and but are not limited to, stand reduction or failure, seed- north Arkansas geographic areas based on yield ling stress and increased production costs. Management potential and management considerations. may overcome many of these risks and must be Recommended Geographic Optimum Absolute weighed against the potential benefits of early planting. Region For this reason, it is recommended that the optimum Begin Cut-off Begin Cut-off time for seeding rice be based on grain yield potential South March 28 May 20 March 20 June 15 Central April 1 May 15 March 25 June 10 and management factors. Therefore, the estimated opti- North April 10 May 10 April 1 June 5 mum seeding dates listed in Table 4-10, based on yield Seeding during the optimum time frame does not guarantee high yields and management, are suggested for grower use. Relative or suggest that crop failure cannot occur when rice is seeded during these times. yield, as affected by seeding date, is presented in Recommended absolute does NOT mean that a successful rice crop Table 4-9 and should be used to make decisions cannot be grown if seeded outside of the dates listed. Success may be evaluated and/or interpreted using various parameters (i.e., cropping concerning the profitability of late-seeded rice systems, management, cash flow, field reclamation, etc.) and may compared to alternate crops. differ among specific cultivars. Specific cultivar recommendations for late-seeded reduce grain yield and quality. The DD50 program, rice (June seeding dates) should be made on yield available at the county Extension office or online at performance in seeding date studies, seed availability http://dd50.uaex.edu/dd50Logon.asp, can be used to and planned seeding date. Of the available cultivars estimate heading dates for different cultivars. A range that have been tested in seeding date studies, Bengal, of dates for the occurrence of freezing temperatures in Cypress, Drew, Francis and Wells are recommended several geographic regions is provided in Table 4-11. for late planting. The hybrids developed by RiceTec, Table 4-12 lists the predicted dates for Bengal, Spring Inc. also perform well when planted late. Contact and Wells, emerged on June 1, 15 and 30, to reach your local county Extension agent or refer to the 50 percent heading in northeast (Clay County) and Cooperative Extension Service web page for the latest southeast (Chicot County) Arkansas. Finally, seeding planting date study yield information. date may influence certain diseases. Therefore, disease susceptibility must be considered when selecting a cul- If the estimated date of 50 percent heading is after tivar for early or late seeding. For example, earlier September 10 to 20, rice should not be planted since seeded rice is less likely to suffer severe damage from cool temperatures and possible frost may significantly blast, smuts or bacterial panicle blight diseases but 37

8 Table 4-11. Expected freeze dates for several eastern Arkansas locations. City - County Last Date in Spring with Temp. < 32F First Date in Fall with Temp < 32F Corning - Clay April 4 to April 17 October 11 to October 25 Augusta - Woodruff March 29 to April 14 October 19 to November 2 Pine Bluff - Jefferson March 20 to April 3 October 26 to November 9 Crossett - Ashley April 4 to April 16 October 22 to November 2 Freeze dates were obtained from county soil surveys and are the dates for which temperatures below 32F first or last occur in one to five out of every ten years. Time period from 1951 to 1974. Time period from 1951 to 1990. Table 4-12. Expected 50% heading dates of Bengal, Spring and Wells rice cultivars in southeast, central and northeast Arkansas for three June emergence dates. Predicted 50% Heading Date Emergence Date Cultivar Chicot County Prairie County Clay County June 1 Bengal August 10 August 13 August 14 Spring August 3 August 3 August 4 Wells August 10 August 14 August 15 June 15 Bengal August 22 August 27 August 27 Spring August 15 August 15 August 17 Wells August 23 August 28 August 28 June 30 Bengal September 8 September 12 September 14 Spring August 31 August 31 September 5 Wells September 8 September 13 September 14 Predictions are for 50% heading using the 30-year weather temperature means. Add 35 to 45 days for estimates of 20% grain moisture. may have increased sheath blight problems compared tillage operations to help eliminate small depressions to late-seeded rice. and high spots in fields. Tillage practices implemented in conventional tilled fields may include a disk, field Tillage and Post-Seeding cultivator, roller and a land plane or float. Tillage Management requirements differ among soil textures, previous crop and field condition after previous crop harvest. An In Arkansas, the most common method of seeding excellent seedbed can be prepared on most sandy and rice is direct, dry seeding using a drill, airplane or air- silt loam soils with minimal tillage. Tillage on clay flow truck. Broadcast seeding is most commonly used soils usually produces a cloddy seedbed that does not on clay soils or in wet years when speed of planting is provide good seed-to-soil contact. Stale seedbed or no- important. Dry, broadcast-seeded rice is covered either till seeding usually improves seed-to-soil contact on by a final tillage operation or by flushing after levees clay soils. The use of a roller before or behind the drill are pulled. Dry seeding is practiced on about 94 per- often improves seed-to-soil contact and speeds emer- cent of the Arkansas rice acreage. The remaining gence by compacting the soil. This is best illustrated 6 percent is water-seeded rice. by field observations seen each spring where rice first The use of reduced tillage practices has increased in emerges in truck or tractor tire tracks. Research has rice production over the past ten years. Reduced shown that rolling behind drilled or broadcast-seeded tillage practices may be more appropriately divided rice can increase stand population (Table 4-13). into two groups including stale seedbed (soil is tilled and floated in fall or late winter) or true no-till (rice is Management Key planted in previous crop stubble). A level seedbed free of potholes and excessive stubble or trash is desired, Establish a smooth field surface that provides a regardless of tillage and seeding method. A land plane good seedbed, drainage and water control. or float is commonly used two times in conventional 38

9 Table 4-13. Influence of rolling behind drill on final better growth and production of rice in the barrow rice stand density on a Perry clay soil at the ditches. Levees are typically seeded on the final one to Southeast Branch Experiment Station, located near Rohwer, Arkansas. two passes with a levee disk that has a broadcast seeder. A levee gate should be installed in each levee Cultivar Rolled Non-rolled by pushing out a section of soil in the direction of Seedlings/ft2 Bond 21 17 water flow. The ability to manage water is essential for Lemont 21 16 all rice crop management practices. Construction of Seeding rate was 40 seed/ft2 for each cultivar. levees and gate installation should be performed as soon after planting as possible to enable flushing or Generally, levees should be surveyed on 0.2 foot flooding and to aid in stand establishment or pest vertical intervals for proper water management. management practices. Additional information on However, if a field is very flat and a single levee may irrigation of rice will be covered in Chapter 10, contain more than 10 acres, levees should be marked Water Management. on 0.1 foot intervals to facilitate flooding. Rice fields having considerable slope may require that levees be surveyed on 0.3 to 0.4 foot intervals to reduce the Management Key number of levees. Levees may be surveyed and marked An accurate levee survey is critical to being able before or after seeding. Surveying levees in minimum to manage water effectively and efficiently later in tillage and no-till systems during the fall, winter or the season. early spring spreads out labor requirements that are typically encountered following planting operations. Levee formation may be completed with two to eight Rice harvest must be considered in planting and passes with a levee disk, depending on soil texture. A cultivar selection to ensure that rice matures over a couple of hours for drying may be required between range of dates and allows for timely harvest. Rice that levee disk passes for clay soils. On clay soils using is planted during a three-week period in April may reduced tillage practices, a levee base may be pulled mature and be ready for harvest at the same time. Rice after surveying in fall, winter or early spring to can be planted much quicker than it can be harvested. minimize water seepage losses. Therefore, spread out planting dates to help spread out harvest. Levee squeezers have been widely adopted and provide some benefits over a conventional levee disk. Table 4-14 lists the estimated dates of 20 percent grain Barrow ditches are typically not as deep, resulting in moisture for five cultivars that differ in maturity. Table 4-14. Influence of emergence date on predicted dates for 20% grain moisture for five cultivars using 30-year weather norms for Stuttgart, Arkansas. Rice Emergence Date Cultivar April 15 April 25 May 5 May 15 May 25 June 5 June 15 June 25 Predicted Date for 20% Grain Moisture Spring Aug. 12 Aug. 17 Aug. 19 Aug. 25 Sept. 1 Sept. 14 Sept. 23 Oct. 3 Jefferson Aug. 16 Aug. 22 Aug. 23 Aug. 29 Sept. 10 Sept. 18 Sept. 27 Oct. 8 Cocodrie Aug. 21 Aug. 26 Aug. 27 Sept. 8 Sept. 14 Sept. 23 Oct. 3 Oct. 13 Wells Aug. 23 Aug. 28 Aug. 29 Sept. 9 Sept. 16 Sept. 25 Oct. 4 Oct. 15 Bengal Sept. 1 Sept. 11 Sept. 12 Sept. 19 Sept. 25 Oct. 4 Oct. 14 Oct. 24 Approximate date of 50% heading can be estimated by subtracting 35 days from listed date for Spring, Jefferson, Cocodrie and Wells or 45 days for Bengal. 39

10 References Counce, P.A. 1989. Row Spacing effects on rice yields. Ark. Agric. Exp. Stn. Rep. Ser. 313, Fayetteville. Counce, P.A. 1987. Asymptotic and parabolic yield and linear nutrient content responses to rice pop- ulation density. Faw, W.F., and T.H. Johnston. 1975. Effect of seeding date on growth and performance of rice varieties in Arkansas. Ark. Agric. Exp. Stn. Rep. Ser. 224, Fayetteville. Faw, W.F., and T.K. Porter. 1981. Effect of seeding rate on performance of rice varieties. Ark. Agric. Exp. Stn. Rep. Ser. 287, Fayetteville. Frizzell, D.L., C.E. Wilson, Jr., R.J. Norman, N.A. Slaton, A.L. Richards, J.L. Hill, J.W. Branson, and S.K. Runsick. 2006. Influence of row spacing and seeding rate on rice grain yield. p. 270-275. In (R.J. Norman et al., (ed) B.R. Wells Rice Research Studies 2005. Ark. Agr. Exp. Sta. Res. Ser. 540. Gravois, K.A., and R.S. Helms. 1998. Seeding date effect on rough rice yield and head rice and selec- tion for stability. Euphytica 102:151-159 Jones, D.B., and G.H. Snyder. 1987. Seeding rate and row spacing effects on yield and yield components of drill-seeded rice. Agron. J. 79:623-626. Runsick, S.K., C.E. Wilson, Jr., A.L. Richards, J.W. Branson, and J.L. Hill. 2006. Influence of seeding rate on grain yield and milling yield of five rice cultivars in Arkansas. p. 304-309 In (R.J. Norman et al., (ed) B.R. Wells Rice Research Studies 2005. Ark. Agr. Exp. Sta. Res. Ser. 540. Slaton, N.A., R.S. Helms, H.M. Chaney, C.A. Stuart, and T.E. Windham. 1991. Results of the rice research verification trials, 1990. AG94-9-91. Univ. of Ark. Coop. Ext. Serv., Little Rock. 40

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